1. Field of the Invention
The present invention relates to a process for preparing 4'-methyl-2-cyanobiphenyl. More particularly, the present invention relates to a process for preparing 4'-methyl-2-cyanobiphenyl, which is useful as an intermediate of 4'-bromomethyl-2-cyanobiphenyl used as starting materials of pharmaceuticals such as antihypertensives, and also relates to a process for regenerating 4'-methyl-2-cyanobiphenyl from by-products formed during the preparation of 4'-bromomethyl-2-cyanobiphenyl from 4'-methyl-2-cyanobiphenyl.
2. Discussion of the Related Art
Conventionally, there have been known a process for preparing 4'-bromomethyl-2-cyanobiphenyl, comprising dissolving 4'-methyl-2-cyanobiphenyl in a solvent; brominating the 4'-methyl-2-cyanobiphenyl; crystallizing the resulting 4'-bromomethyl-2-cyanobiphenyl; and collecting the resulting crystals by filtration as disclosed in U.S. Pat. No. 5,621,134, corresponding to Japanese Patent Laid-Open No. Hei 8-127562.
In the above process, there are some advantageous merits in being able to industrially and advantageously prepare 4'-bromomethyl-2-cyanobiphenyl from inexpensive starting materials in a high yield.
However, in the above process, after crystallizing 4'-bromomethyl-2-cyanobiphenyl from the reaction mixture and collecting the obtained crystals by filtration, the resulting filtrate contains 4'-dibromomethyl-2-cyanobiphenyl as a by-product as well as 4'-bromomethyl-2-cyanobiphenyl which remains in a mother liquor.
Therefore, the development of a process of efficiently reusing the by-product, 4'-dibromomethyl-2-cyanobiphenyl and the remaining desired compound, 4'-bromomethyl-2-cyanobiphenyl contained in the filtrate has been highly desired.
In view of the problems in the prior art mentioned above, an object of the present invention is to provide a process of efficiently reusing the by-product, 4'-dibromomethyl-2-cyanobiphenyl and the remaining desired compound, 4'-bromomethyl-2-cyanobiphenyl contained in the filtrate.
These and other objects of the present invention will be apparent from the following description.